1. Field of the Invention
The present invention relates to a system and method for controlling an internal combustion engine based on exhaust back pressure.
2. Background Art
A number of strategies have been developed to reduce emissions for truck, automotive, and stationary engines used in power plants. In addition to controlling the basic combustion process using an electronic control module to balance trade-offs between performance and emissions, emission control devices are often placed in the exhaust stream to reduce or eliminate the byproducts of incomplete combustion. A particulate trap or filter is an emission control device placed in the exhaust stream to reduce particulate emissions, which are primarily carbon particles or soot. As more particulates accumulate in the filter or trap, the increasing restriction to exhaust flow results in a gradual increase in exhaust back pressure, i.e. the pressure within the exhaust upstream of the filter. If the trap is not properly maintained or if engine conditions prevent the trap from being regenerated, the exhaust back pressure may increase to a point which could jeopardize engine component life.
Exhaust back pressure may be affected by engine components other than emission control devices. For example, exhaust back pressure may be controlled to achieve a desired EGR flow using a turbocharger, such as a variable geometry turbocharger (VGT). Likewise, exhaust back pressure may be controlled to modulate engine braking. As such, any anomalous operation of various engine components may result in a gradual or sudden increase in exhaust back pressure which could be detrimental to a number of engine components.
An object of the present invention is to provide a system and method for controlling an engine to reduce or prevent component damage from excessive exhaust back pressure.
Another object of the present invention is to provide a system and method for monitoring a particulate trap or filter using a pressure sensor to monitor exhaust pressure and reduce available engine torque when the exhaust pressure exceeds a predetermined or adaptable threshold.
A further object of the present invention is to provide a system and method for detecting tampering with an emission control device.
An additional object of the present invention is to provide a system and method for alerting an operator and/or maintenance personnel to an increased exhaust pressure so corrective action can be initiated before component damage occurs.
In carrying out the above objects and other objects, features, and advantages of the present invention, a system and method for controlling an internal combustion engine include monitoring exhaust pressure and reducing engine output when the exhaust pressure exceeds a threshold to reduce or prevent engine component damage from excessive exhaust pressure. In one embodiment, the exhaust pressure is monitored to detect tampering with a component in the emission control system, such as a pressure sensor or particulate trap or filter, for example.
The present invention provides a number of advantages relative to the prior art. For example, the present invention monitors exhaust pressure to reduce or prevent damage to engine components due to excessive pressure, rather than simply indicating that the particulate filter or trap may be plugged. In one embodiment, the present invention preferably warns the operator when exhaust back pressure exceeds a first threshold to provide an opportunity to take corrective action. If the condition is not corrected, available engine torque is reduced, which provides an increased incentive for the operator to remedy the problem before significant damage occurs. Furthermore, reducing engine output as back pressure increases is self-correcting in that the lower engine output has an associated lower pressure, which in turn reduces the likelihood of component damage.
The above advantages, and other advantages, objects, and features of the present invention are readily apparent from the following detailed description of the best mode for carrying out the invention when taken in connection with the accompanying drawings.